Apparatus for forming ribbon with lateral force means



Oct. 31, 1967 M. w. BARRETT ET AL 3,350,188

APPARATUS FOR FORMING RIBBON WITH LATERAL FORCE MEANS Original Filed June 2, 1964 2 Sheets-Sheet l o INVENTORS MARLIN w. BARRETT new a. amen, 5, E0688 8- OLTMAN GWWMW Arron/v vs Oct. 31, 1 967 M. w. BARRETT ET 3,350,188

APPARATUS FOR FORMING RIBBON WITH LATERAL FORCE MEANS Original Filed June 2, 1964 2 Sheets-Sheet 2 WWHS M ATTOR NE Y5 United States Patent 3,350,188 APPARATUS FOR FORMING RIBBON WITH LATERAL FOR-CE MEANS Marlin W. Barrett, Fresno, Calif., Dean G. Cramer, Festus, Mo., and Roger B. Oltman, Natrona Heights, Pa., assignors to Pittsburgh Plate Glass Company, Pittsburgh, Pa., a corporation of Pennsylvania Original application June 2, 1964, Ser. No. 372,068. Divided and this application Nov. 14, 1966, Ser. No. 593,758

4 Claims. (Cl. 65-165) This application is a division of our co-pending application, Ser. No. 372,068, filed June 2, 1964, now abandoned, entitled Method and Apparatus for Manufacturing Glass.

This invention relates to a method of and apparatus for the manufacturing of glass and more specifically to the treatment of a formed ribbon of glass as it is cooled and conveyed along a pretermined path.

In the manufacture of flat glass, ribbons of glass are formed by any one of a number of known processes and conveyed from the forming area through an annealing zone and thence to a cutting station where the ribbon is cut into sheets. The ribbon may be conveyed vertically or first vertically and then horizontally, as in some window glass drawing operations, or may be conveyed horizontally, as in plate glass and float glass operations. In some plate glass operations grinding or both grinding and polishing of the ribbon may be done intermediate the annealing zone and cutting station. In all such continuous operations, the ribbon of glass is at a relatively high temperature (i.e., around 2000 degrees Fahrenheit and above) immediately after being formed and is cooled to a relatively low temperature (i.e., around 300 degrees Fahrenheit or lower) prior to cutting. In most operations the ribbon is gradually cooled in a controlled manner through the annealing range of the glass and thereafter is allowed to cool naturally.

A ribbon of glass at temperatures near the lower limit of the annealing range and below (e.g., about 950 degrees Fahrenheit and below) is solidified to the extent that there is little or no viscous flow of the glass due to thermal or physical stresses. Hence, at these temperatures, the ribbon is capabale of cracking or splitting and, in fact, often does crack or split, particularly due to stresses caused by uneven cooling. When these splits occur down the central portion of the ribbon, parallel to the direction of ribbon travel, they often extend from the end of the ribbon at the cutting station back to the annealing zone, often a distance of over 200 feet. Furthermore, unless steps are taken to heal the split, it may exist for several days, resulting in the loss of all the glass during such period. The current method of healing such splits is to place a heated brick upon the ribbon upstream of the split and in a location where it is estimated the split will occur when that portion of the ribbon supporting the brick reaches the location of where the split is being generated. While this approach is a relatively effective cure for an existing split, it in no way prevents a subsequent split from starting. It is not uncommon to experience an average of about one split every day on a single line, with the length of the splits averaging more than 175 feet. Considering a standard ribbon width of between 8 to 12 feet, a considerable amount of glass is wasted due to ribbon splits.

The present invention provides a method of and apparatus for reducing the number of splits that occur during the manufacture of a continuous ribbon of glass. Broadly, this is accomplished by applying compressive forces against the lateral edges of the moving ribbon. The forces are applied at locations where the ribbon is sufficiently cool to resist substantial deformation by the forces and, by the same token, where the ribbon would be apt to split. This location may be determined empirically once a split occurs by observing the location where the split is being generated and applying forces somewhat downstream therefrom.

Most advantageously, the forces will be applied toward each other from locations opposite each other across the ribbon and in the plane of the ribbon. In many instances it is desirable to apply such forces at two or more locations along the ribbon, between the annealing lehr and the cutting station.

More specifically, the present invention contemplates continuously applying compressive forces against the edges of the ribbon at one or more locations along the ribbon length in the area of the ribbon where the glass temperature is below the upper limit of the annealing range of the glass and usually below the lower limit of the annealing range. The forces may be conveniently applied by biasing horizontally disposed wheels, freely rotatable about vertical axes, against the longitudinally extending edge thickness of the ribbon. It will be understood that, to the extent the magnitudes of the biasing forces applied by oppositely disposed wheels are separately controlled, the position of the moving ribbon along the conveying path may be altered and controlled.

The attendant advantages of this invention and the various embodiments thereof will be readily appreciated as the same become better understood by reference to the following detailed description when considered in connection with the accompanying drawings in which:

FIG. 1 is a diagrammatic plan view of a ribbon forming machine including a tank, forming rolls, continuous glass ribbon, conveyor and annealing lehr and showing apparatus for applying forces to the longitudinally extending edges of the ribbon;

FIG. 2 is a detail plan view of a preferred embodiment for applying a controlled force to an edge of a moving ribbon of glass; and

FIG. 3 is an end elevation view of the apparatus of FIG. 2.

Referring now to FIG. 1, there is shown a conventional glass melting tank 10 having a pair of rotatably driven forming rolls 12 and 13 at the exit end for forming a. continuous ribbon 15 from molten glass produced in the tank. A series of spaced, aligned conveying rolls 16 form an apron 18, inclined downward and forward from the forming rolls 12 and 14 for receiving the formed ribbon, and then form a horizontal conveyor 20, driven in a manner well known in the art, for carrying the ribbon in straight line travel away from the forming rolls. A portion of conveyor 20 just subsequent to the apron 18 in the direction of ribbon travel is enclosed by an annealing lehr 22 that controls the rate of cooling of the ribbon in a known manner through the critical annealing range of the glass. The remainder of the conveyor 20 is open to the general surroundings of the plant and, in the embodiment shown,

leads to a cutting station (not shown) where the continuous ribbon 15 is cut transversely into separate sheets. The above-described arrangement is conventional and well known in the art.

At the mouth or exit end of the annealing lehr 22 is a first mechanism, indicated generally at 24, for applying forces against opposite, longitudinally extending edges of the ribbon. In the preferred embodiment of the present inv'ention, an optional second mechanism, indicated generally at 26, and identical to the first, is located downstream from the first mechanism. Because each mechanism is identical in structure and function, only one will be described in detail.

Referring now to FIGS. 1-3 and with reference to the mechanism designated'generally at 24, a cross beam 28 supported by stanchions 30 and 31 spans conveyor 20 above ribbon 15. Brackets 32 and 33 are attached to and supported by cross beam 28, one adjacent each edge of ribbon 15. Because the structure supported by each bracket 32 and 33 is identical, one being in mirror image relationship to the other, only the structure supported by bracket 32 will be described in detail.

An arm 34 is pivotally supported by a vertical stub staft 36 of bracket 32. A vertical pin 38 having an upper bearing flange 39 is journaled for rotation in the distal end of arm 34 and extends downward through the plane of the glass ribbon but beyond the longitudinal edge of the ribbon. A disc or wheel 40 is fastened to the lower extremity of pin 38, as by lock bolts 41 and 42 cooperating with a threaded portion 43 of pin 38. The wheel may be formed of a somewhat resilient material such as relatively hard rubber or polyurethane, or may be formed of a suitable metal or metal alloy. The position of stub shaft 36, the length of link 34 and the diameter of wheel 40 are selected to allow the peripheral edge of wheel 40 to be moved in the plane of ribbon 15 into and out of engagement with the edge thickness of the ribbon.

Attached to an upper threaded portion 44 of pin 38 is one end of a link 46. The opposite end of link 46 extends above the edge of ribbon 15 and is attached to a clevis 48. A rod 50 extending from the clevis 48 is attached by a coupling 52 to the end of a piston rod 54 of a conventional double piston, double acting air cylinder 56 that is attached by a bracket 58 to the cross beam 28 centrally of the ribbon 15. To bias wheel 40 against the ribbon edge, air pressure is supplied to cylinder 56 through inlet 60, withdrawing piston rod 54 and transmitting the force to wheel 40 through rod 50 and link 46. The counterpart wheel 41 adjacent the opposite edge of the ribbon 15 is actuated by supplying air through inlet 61 of cylinder 56 to withdraw the other piston rod 55 of cylinder 56 extending in the opposite direction and coupled to wheel 41 in the same manner described above in connection with wheel 40. The biasing force is released by connecting cylinder inlets 60 and 61 to exhaust and connecting an exhaust outlet 62 to the source of air pressure in a conventional, known manner. The pressure to each inlet 60 and 61 may be individually controlled in a manner well known in the art to initially apply different pressures to each side of the ribbon as an aid to controlling the ribbon location.

Operation The following is an example, by way of illustration only, of a preferred mode of operation of the invention disclosed herein as applied to a conventional plate glass rolling operation:

A ribbon of conventional soda-lime-silica glass is formed from a molten bath of glass in tank 10 by forming rolls 12 and 14, the ribbon being formed to a width of approximately 134 inches and a thickness of approximately A inch. The ribbon is first supported by rolls 16 of apron 18 and then by horizontal conveyor and is conveyed through a conventional annealing lehr 22 and thence to a cutting station (not shown) at a speed of approximately 130 to 155 inches per minute. The ribbon, as initially formed is at a temperature of approximately 2000 degrees Fahrenheit and is allowed to cool naturally to approximately 1200 to 1300 degrees Fahrenheit, close to the upper temperature limit of the annealing range before entering the annealing lehr 22. The ribbon is cooled in a gradual and controlled manner through the critical annealing range of the glass as it passes through the annealing lehr 22, which is about 200 feet long. For ordinary soda-lime-silica plate glass, the upper limit of the annealing range is generally considered to be between about 1080 to 1100 degrees Fahrenheit and the lower limit between about 920 to 950 degrees Fahrenheit, the annealing range being generally dependent upon the rate of cooling and time available for annealing. In general, the

upper limit of the annealing range is considered to be the lowest temperature at which the relaxation of stresses is so rapid that stresses cannot be detected on the time scale of the process being considered. The lower limit is considered to be that temperature from which a piece of glass can be quickly cooled without introducing permanent stress. In the present example, the ribbon does not exit from annealing lehr 22 until the temperature of the ribbon is about 500 degrees Fahrenheit or lower.

A pair of wheels 40 and 41 with a peripheral portion of relatively hard polyurethane are located at the mouth or exit end of lehr 22 at each longitudinally extending edge of the ribbon. Each wheel is rotatable about a vertical axis and is located in the plane of ribbon 15 and in peripheral contact with the adjacent edge of ribbon 15. The air cylinder 56 remains actuated during the manufacture of a ribbon 15 to retract piston rods 54 and 55 into each end of the cylinder to bias wheels 40 and 41 that are connected with the piston rods against the longitudinally extending edges of the ribbon. The wheels should exert sufiicient force against the ribbon edges to hold the edges in fixed relationship to each other to prevent the ribbon from separating lengthwise as it normally does when a split occurs. In the device of the present example, a double piston-air cylinder having an effective bore of 2 inches and a piston stroke of 9 inches for each piston has been found suitable for the intended purpose of providing compressive forces against the edge thickness of the glass ribbon when supplied with air under a pressure of about 20 to 30 pounds per square inch gauge. This arrangement, as shown in FIGS. 1-3, allows each wheel 40 and 41 to be pivoted away from contact with the ribbon edges when desired, a distance of about 3 inches. The force transmitting linkage from piston to wheel is substantially direct, i.e., in a straight line, except for a slight angular relationship between link 46 and rod 50. Wheels 40 and 41 are approximately 6% inches in diameter. While wheels 40 and 41 exert continual pressure against the edges of the ribbon by virtue of the air pressure introduced into cylinder 56 through inlets 60 and 61, the pressure may be readily released and the wheels removed from contact with the ribbon edges by reversing the air pressure to each piston of double ended cylinder 56.

A second pair of rolls of identical construction and operated in an identical manner to those at the mouth or exit end of lehr 22 are optionally positioned approximately 40 feet further downstream from the mouth of the annealing lehr and about 10 feet upstream of the cutting station.

It has been found, when using the apparatus in the manner above described, that not only is the number of splits that occur reduced, but also even when a split does occur, the pressure applied by the wheels adjacent each edge of the moving ribbon prevents the split from opening up, as it normally does to a width of approximately 1 inch or more at its widest point. In some instances this stops the continual generation of the split, permitting the split portion to move forward to the cutting station, thereby overcoming the difiiculty.

In the operation of a plate glass rolling tank to produce a ribbon in the manner above described and using a single pair of wheels biased against the longitudinally extending edges of the moving ribbon at the mouth or exit end of the annealing lehr to apply a compressive force as above described, a substantial improvement in ribbon production was experienced. Disregarding splits under 25 feet in length, which are normally considered as cross-breaks, a total of 161 splits were experienced during a period of 159 days in the normal manufacture of a continuous ribbon, as described above but without the use of edge compressive forces as provided by the present invention. The average length of each split was 156 fzet with a total loss of 25,144 linear feet of glass. After a pair of wheels, as described above, was installed at the exit end of the annealing lehr and operated in the manner above described to apply forces to the edge-s of the ribbon, a total of 89' splits occurred during a period of 180 days, with an average length of split of 125.8 feet, resulting in a glass loss of 11,187 linear feet. Thus, the use of the present invention resulted in a reduction in the length of .the splits occurring of 19.4 percent, a reduction in the frequency of split occurrence of 51.1 percent, and a reduction of average glass losses per day of 60.7 percent.

Variations While the apparatus and operating example disclosed above illustrate a preferred embodiment of this invention, it will be understood that other apparatus may be utilized in many instances without departing from the inventive concept.

While the preferred embodiment of this invention utilizes two spaced pairs of wheels biased inwardly against the longitudinally extending margins of the moving glass ribbon, one such pair has been found to provide a substantial improvement in reducing the number of splits occurring in a ribbon and the length of such splits. It should be understood, of course, that any additional number of such pairs may beutilized. While the general location of the wheels is important, the precise location of such pairs of wheels is not critical. More specifically, the forces should be applied at a position along the ribbon where the ribbon temperature has been reduced to at least below the upper limit of the annealing range, preferably to below the lower limit of the annealing range, both to prevent deformation of the ribbon due to the compressive force exerted by the wheels and also to assure that the wheels exert their force at a location Where a split otherwise might occur. Particularly, satisfactory results have been experienced with the form applied to portions of the ribbon at temperatures below the annealing range, usually to portions at temperatures in the range of 500 to 300 degrees Fahrenheit.

While freely rotating wheels are believed most advantageous for applying the desired forces to the edges of the ribbon, other mechanism, including smooth, nonrotating bearing surfaces in slidable contact wtih the ribbon edges may be used. Furthermore, other force exerting means for biasing the edge contacting members against the ribbon may be used in lieu of the specifically disclosed air cylinder and linkages; for example, springs or hand operated toggle-joint levers may be used.

This invention has been used successfully on ribbons of various thicknesses, including thicknesses of A3, A1, 7 and In general more pressure should be applied by the rolls where a thicker ribbon is being manufactured. Air pressures as low as pounds per square inch gauge have been used with the above-described apparatus of the operating example when producing glass ribbon inch thick, and as high as 40 pounds per square inch gauge with ribbons /2 inch thick.

The present invention has application to ribbons formed by other processes than the rolling process specifically disclosed and, in addition, is also useful for guiding or changing the location of a ribbon along the path of travel, either in conjunction with applying compressive forces to the edges or separately therefrom. It will be understood that the formed ribbon need not be supported by space rolls along the path of travel as specifically disclosed, but may be supported on other supports such as a fluid support, for example, a flow of gas from a support bed or a molten metal bath.

It should be evident from the above section that while in the foregoing disclosure certain preferred embodiments of the invention have been disclosed, numerous modifications or alterations may be made therein Without departing from the spirit and scope of the invention as set forth in the appended claims.

We claim: 1. An apparatus for continuously forming a ribbon of glass comprising,

means for supporting and conveying a continuously formed ribbon of glass in a substantially horizontal plane, said ribbon of glass having side edge surfaces,

means for continuously conveying said ribbon of glass along said supporting means, means for cooling said continuously formed ribbon of glass through the annealing range of said glass as the ribbon is conveyed along said supporting means,

means for applying pressure simultaneously to said ribbon of glass at aligned, oppositely disposed locations in the edge surfaces thereof along a line lying in a plane of said ribbon of glass,

means for movably supporting said pressure applying means for simultaneous movement toward and away from said edge surfaces;

said pressure applying means being adapted to exert sufiicient force to said edge surfaces to prevent outward lateral movement thereof,

whereby a split formed and extending longitudinally in said ribbon of glass is not permitted to advance.

2. An apparatus as described in claim 1 wherein said means for applying pressure to the edge surfaces of said ribbon of glass each comprises a rotatably mounted Wheel disposed on opposite sides of said ribbon of glass.

3. An apparatus as described in claim 1 wherein said means for applying pressure to the edge surfaces of said ribbon of glass each comprises a movable member slidably engaging the edge surfaces of said ribbon of glass.

4. An apparatus as described in claim 1 having fluid pressure means for simultaneously actuating said means for applying pressure simultaneously to the edge surfaces of said ribbon of glass.

References Cited UNITED STATES PATENTS 1,548,104 8/1925 Slinglaff 29 2,298,348 10/1942 Coxe 65182 3,001,680 9/1961 Nitkiewicz 22615 FOREIGN PATENTS 1,362,013 4/ 1964 France.

DONALL H. SYLVESTER, Primary Examiner. F. W. MIGA, Assistant Examiner. 

1. AN APPARATUS FOR CONTINUOUSLY FORMING A RIBBON OF GLASS COMPRISING, MEANS FOR SUPPORTING AND CONVEYING A CONTINUOUSLY FORMED RIBBON OF GLASS IN A SUBSTANTIALLY HORIZONTAL PLANE, SAID RIBBON OF GLASS HAVING SIDE EDGE SURFACES, MEANS FOR CONTINUOUSLY CONVEYING SAID RIBBON OF GLASS ALONG SAID SUPPORTING MEANS, MEANS FOR COOLING SAID CONTINUOUSLY FORMED RIBBON OF GLASS THROUGH THE ANNEALING RANGE OF SAID GLASS AS THE RIBBON IS CONVEYED ALONG SAID SUPPORTING MEANS, MEANS FOR APPLYING PRESSURE SIMULTANEUOSLY TO SAID RIBBON OF GLASS AT ALIGNED, OPPOSITELY DISPOSED LOCATIONS IN THE EDGE SURFACES THEREOF ALONG A LINE LYING IN A PLANE OF SAID RIBBON OF GLASS, MEANS FOR MOVABLY SUPPORTING SAID PRESSURE APPLYING MEANS FOR SIMULTANEOUS MOVEMENT TOWARD AND AWAY FROM SAID EDGE SURFACES. SAID PRESSURE APPLYING MEANS BEING ADAPTED TO EXERT SUFFICIENT FORCE TO SAID EDGE SURFACES TO PREVENT OUTWARD LATERAL MOVEMENNT THEREOF, WHEREBY A SPLIT FORMED AND EXTENDING LONGITUDINALLY IN SAID RIBBON OF GLASS IS NOT PERMITTED TO ADVANCE. 